Implement autoplay gesture override experiment.

Source/core/html/HTMLMediaElement.cpp

 /*
  * Copyright (C) 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 229 matching lines @@
     // when used with parameters, e.g. "application/octet-stream;codecs=theora", is a type that the user agent knows
     // it cannot render.
     if (contentMIMEType != "application/octet-stream" || contentTypeCodecs.isEmpty()) {
         WebMimeRegistry::SupportsType supported = Platform::current()->mimeRegistry()->supportsMediaMIMEType(contentMIMEType, contentTypeCodecs, keySystem.lower());
         return supported > WebMimeRegistry::IsNotSupported;
     }
 
     return false;
 }
 
-// These values are used for a histogram. Do not reorder.
-enum AutoplayMetrics {
-    // Media element with autoplay seen.
-    AutoplayMediaFound = 0,
-    // Autoplay enabled and user stopped media play at any point.
-    AutoplayStopped = 1,
-    // Autoplay enabled but user bailed out on media play early.
-    AutoplayBailout = 2,
-    // Autoplay disabled but user manually started media.
-    AutoplayManualStart = 3,
-    // Autoplay was (re)enabled through a user-gesture triggered load()
-    AutoplayEnabledThroughLoad = 4,
-    // Autoplay disabled by sandbox flags.
-    AutoplayDisabledBySandbox = 5,
-    // This enum value must be last.
-    NumberOfAutoplayMetrics,
-};
-
-static void recordAutoplayMetric(AutoplayMetrics metric)
+void HTMLMediaElement::recordAutoplayMetric(AutoplayMetrics metric)
 {
     Platform::current()->histogramEnumeration("Blink.MediaElement.Autoplay", metric, NumberOfAutoplayMetrics);
 }
 
 WebMimeRegistry::SupportsType HTMLMediaElement::supportsType(const ContentType& contentType, const String& keySystem)
 {
     DEFINE_STATIC_LOCAL(const String, codecs, ("codecs"));
 
     if (!RuntimeEnabledFeatures::mediaEnabled())
         return WebMimeRegistry::IsNotSupported;
@@ skipping 69 matching lines @@
     , m_sentEndEvent(false)
     , m_closedCaptionsVisible(false)
     , m_completelyLoaded(false)
     , m_havePreparedToPlay(false)
     , m_tracksAreReady(true)
     , m_haveVisibleTextTrack(false)
     , m_processingPreferenceChange(false)
     , m_remoteRoutesAvailable(false)
     , m_playingRemotely(false)
     , m_isFinalizing(false)
-    , m_initialPlayWithoutUserGestures(false)
+    , m_initialPlayWithoutUserGesture(false)
     , m_autoplayMediaCounted(false)
     , m_inOverlayFullscreenVideo(false)
     , m_audioTracks(AudioTrackList::create(*this))
     , m_videoTracks(VideoTrackList::create(*this))
     , m_textTracks(nullptr)
 #if ENABLE(WEB_AUDIO)
     , m_audioSourceNode(nullptr)
 #endif
+    , m_autoplayHelper(*this)
 {
 #if ENABLE(OILPAN)
     ThreadState::current()->registerPreFinalizer(this);
 #endif
     ASSERT(RuntimeEnabledFeatures::mediaEnabled());
 
     WTF_LOG(Media, "HTMLMediaElement::HTMLMediaElement(%p)", this);
 
     if (document.settings() && document.settings()->mediaPlaybackRequiresUserGesture())
         m_userGestureRequiredForPlay = true;
 
     setHasCustomStyleCallbacks();
     addElementToDocumentMap(this, &document);
 }
 
 HTMLMediaElement::~HTMLMediaElement()
 {
     WTF_LOG(Media, "HTMLMediaElement::~HTMLMediaElement(%p)", this);
+
 #if !ENABLE(OILPAN)
     // HTMLMediaElement and m_asyncEventQueue always become unreachable
     // together. So HTMLMediaElement and m_asyncEventQueue are destructed in
     // the same GC. We don't need to close it explicitly in Oilpan.
     m_asyncEventQueue->close();
 
     setShouldDelayLoadEvent(false);
 
     if (m_textTracks)
         m_textTracks->clearOwner();
@@ skipping 289 matching lines @@
     case WebMimeRegistry::IsSupported:
         canPlay = "probably";
         break;
     }
 
     WTF_LOG(Media, "HTMLMediaElement::canPlayType(%p, %s, %s) -> %s", this, mimeType.utf8().data(), keySystem.utf8().data(), canPlay.utf8().data());
 
     return canPlay;
 }
 
+void HTMLMediaElement::recordMetricsIfPausing()
+{
+    // If not playing, then nothing to record.
+    if (!m_playing)

[philipj_slow, 2015/09/02 09:24:12]

Use m_paused here unless there's a reason to use m_playing instead. We shouldn't
have both, and m_playing is the one that we should try to remove.

[liberato (no reviews please), 2015/09/04 06:49:46]

i think i used m_paused originally, but switched after testing the metrics
manually.  i don't remember what case wasn't covered.

i'll re-test and see if there's a way to get the behavior without using
m_playing.

note that i didn't get to this today, and i don't have a device handy to try it
now.  so, i'll revisit tomorrow morning.

[philipj_slow, 2015/09/04 08:42:29]

OK, whatever you find out please let me know, whatever the differences between
m_paused and !m_playing I assume that they are somewhat subtle, which is why I'd
like to get rid of m_playing. (Well, mostly because the spec only has m_paused.)

+        return;
+
+    const bool bailout = isBailout();
+
+    // Record that play was paused.  We don't care if it was autoplay,
+    // play(), or the user manually started it.
+    recordAutoplayMetric(AnyPlaybackPaused);
+    if (bailout)
+        recordAutoplayMetric(AnyPlaybackBailout);
+
+    // If this was a gestureless play, then record that separately.
+    // These cover attr and play() gestureless starts.
+    if (m_initialPlayWithoutUserGesture) {
+        m_initialPlayWithoutUserGesture = false;
+
+        recordAutoplayMetric(AutoplayPaused);
+
+        if (bailout)
+            recordAutoplayMetric(AutoplayBailout);
+    }
+}
+
 void HTMLMediaElement::load()
 {
     WTF_LOG(Media, "HTMLMediaElement::load(%p)", this);
 
-    if (m_initialPlayWithoutUserGestures && m_playing)
-        gesturelessInitialPlayHalted();
+    recordMetricsIfPausing();
 
     if (UserGestureIndicator::processingUserGesture() && m_userGestureRequiredForPlay) {
         recordAutoplayMetric(AutoplayEnabledThroughLoad);
         m_userGestureRequiredForPlay = false;
         // While usergesture-initiated load()s technically count as autoplayed,
         // they don't feel like such to the users and hence we don't want to
         // count them for the purposes of metrics.
         m_autoplayMediaCounted = true;
     }
 
@@ skipping 833 matching lines @@
         shouldUpdateDisplayState = true;
     }
 
     if (m_readyState == HAVE_ENOUGH_DATA && oldState < HAVE_ENOUGH_DATA && tracksAreReady) {
         if (oldState <= HAVE_CURRENT_DATA) {
             scheduleEvent(EventTypeNames::canplay);
             if (isPotentiallyPlaying)
                 scheduleEvent(EventTypeNames::playing);
         }
 
         if (m_autoplaying && m_paused && autoplay()) {

[philipj_slow, 2015/09/02 09:24:12]

Maybe factor this into a shouldAutoplay() that can be used in the other places?

[liberato (no reviews please), 2015/09/04 06:49:46]

Done.

             autoplayMediaEncountered();
 
             if (document().isSandboxed(SandboxAutomaticFeatures)) {
                 recordAutoplayMetric(AutoplayDisabledBySandbox);
-            } else if (!m_userGestureRequiredForPlay) {
-                m_paused = false;
-                invalidateCachedTime();
-                scheduleEvent(EventTypeNames::play);
-                scheduleEvent(EventTypeNames::playing);
+            } else {
+                // If the autoplay experiment says that it's okay to play now,
+                // then don't require a user gesture.
+                m_autoplayHelper.becameReadyToPlay();
+
+                if (!m_userGestureRequiredForPlay) {
+                    m_paused = false;
+                    invalidateCachedTime();
+                    scheduleEvent(EventTypeNames::play);
+                    scheduleEvent(EventTypeNames::playing);
+                }
             }
         }
 
         scheduleEvent(EventTypeNames::canplaythrough);
 
         shouldUpdateDisplayState = true;
     }
 
     if (shouldUpdateDisplayState) {
         updateDisplayState();
@@ skipping 112 matching lines @@
 
     m_lastSeekTime = time;
     m_sentEndEvent = false;
 
     // 10 - Queue a task to fire a simple event named seeking at the element.
     scheduleEvent(EventTypeNames::seeking);
 
     // 11 - Set the current playback position to the given new playback position.
     webMediaPlayer()->seek(time);
 
-    m_initialPlayWithoutUserGestures = false;
+    m_initialPlayWithoutUserGesture = false;
 
     // 14-17 are handled, if necessary, when the engine signals a readystate change or otherwise
     // satisfies seek completion and signals a time change.
 }
 
 void HTMLMediaElement::finishSeek()
 {
     WTF_LOG(Media, "HTMLMediaElement::finishSeek(%p)", this);
 
     // 14 - Set the seeking IDL attribute to false.
@@ skipping 229 matching lines @@
 
 WebMediaPlayer::Preload HTMLMediaElement::effectivePreloadType() const
 {
     return autoplay() ? WebMediaPlayer::PreloadAuto : preloadType();
 }
 
 void HTMLMediaElement::play()
 {
     WTF_LOG(Media, "HTMLMediaElement::play(%p)", this);
 
+    m_autoplayHelper.playMethodCalled();
+
     if (!UserGestureIndicator::processingUserGesture()) {
         autoplayMediaEncountered();
+
         if (m_userGestureRequiredForPlay) {
+            recordAutoplayMetric(PlayMethodFailed);
             String message = ExceptionMessages::failedToExecute("play", "HTMLMediaElement", "API can only be initiated by a user gesture.");
             document().executionContext()->addConsoleMessage(ConsoleMessage::create(JSMessageSource, WarningMessageLevel, message));
             return;
         }
     } else if (m_userGestureRequiredForPlay) {
         if (m_autoplayMediaCounted)
             recordAutoplayMetric(AutoplayManualStart);
         m_userGestureRequiredForPlay = false;
     }
 
@@ skipping 33 matching lines @@
     updateMediaController();
 }
 
 void HTMLMediaElement::autoplayMediaEncountered()
 {
     if (!m_autoplayMediaCounted) {
         m_autoplayMediaCounted = true;
         recordAutoplayMetric(AutoplayMediaFound);
 
         if (!m_userGestureRequiredForPlay)
-            m_initialPlayWithoutUserGestures = true;
+            m_initialPlayWithoutUserGesture = true;
     }
 }
 
-void HTMLMediaElement::gesturelessInitialPlayHalted()
+bool HTMLMediaElement::isBailout() const
 {
-    ASSERT(m_initialPlayWithoutUserGestures);
-    m_initialPlayWithoutUserGestures = false;
-
-    recordAutoplayMetric(AutoplayStopped);
-
     // We count the user as having bailed-out on the video if they watched
     // less than one minute and less than 50% of it.
-    double playedTime = currentTime();
-    if (playedTime < 60) {
-        double progress = playedTime / duration();
-        if (progress < 0.5)
-            recordAutoplayMetric(AutoplayBailout);
-    }
+    const double playedTime = currentTime();
+    const double progress = playedTime / duration();
+    return (playedTime < 60) && (progress < 0.5);
 }
 
 void HTMLMediaElement::pause()
 {
     WTF_LOG(Media, "HTMLMediaElement::pause(%p)", this);
 
     if (m_networkState == NETWORK_EMPTY)
         scheduleDelayedAction(LoadMediaResource);
 
+    m_autoplayHelper.pauseMethodCalled();
+
     m_autoplaying = false;
 
     if (!m_paused) {
-        if (m_initialPlayWithoutUserGestures)
-            gesturelessInitialPlayHalted();
+        recordMetricsIfPausing();
 
         m_paused = true;
         scheduleTimeupdateEvent(false);
         scheduleEvent(EventTypeNames::pause);
     }
 
     updatePlayState();
 }
 
 void HTMLMediaElement::requestRemotePlayback()
@@ skipping 72 matching lines @@
 
 void HTMLMediaElement::setMuted(bool muted)
 {
     WTF_LOG(Media, "HTMLMediaElement::setMuted(%p, %s)", this, boolString(muted));
 
     if (m_muted == muted)
         return;
 
     m_muted = muted;
 
+    m_autoplayHelper.mutedChanged();
+
     updateVolume();
 
     scheduleEvent(EventTypeNames::volumechange);
 }
 
 void HTMLMediaElement::updateVolume()
 {
     if (webMediaPlayer())
         webMediaPlayer()->setVolume(effectiveMediaVolume());
 
@@ skipping 611 matching lines @@
             if (!m_mediaController && !m_paused) {
                 // changes paused to true and fires a simple event named pause at the media element.
                 m_paused = true;
                 scheduleEvent(EventTypeNames::pause);
             }
             // Queue a task to fire a simple event named ended at the media element.
             if (!m_sentEndEvent) {
                 m_sentEndEvent = true;
                 scheduleEvent(EventTypeNames::ended);
             }
+            recordMetricsIfPausing();
             // If the media element has a current media controller, then report the controller state
             // for the media element's current media controller.
             updateMediaController();
         }
     } else {
         m_sentEndEvent = false;
     }
 
     updatePlayState();
 }
@@ skipping 200 matching lines @@
             // The media engine should just stash the rate and muted values since it isn't already playing.
             webMediaPlayer()->setRate(effectivePlaybackRate());
             updateVolume();
             webMediaPlayer()->play();
         }
 
         if (mediaControls())
             mediaControls()->playbackStarted();
         startPlaybackProgressTimer();
         m_playing = true;
+        recordAutoplayMetric(AnyPlaybackStarted);
 
     } else { // Should not be playing right now
         if (isPlaying)
             webMediaPlayer()->pause();
         refreshCachedTime();
 
         m_playbackProgressTimer.stop();
         m_playing = false;
         double time = currentTime();
         if (time > m_lastSeekTime)
@@ skipping 99 matching lines @@
         mediaControls()->refreshCastButtonVisibilityWithoutUpdate();
 
     if (layoutObject())
         layoutObject()->setShouldDoFullPaintInvalidation();
 }
 
 void HTMLMediaElement::stop()
 {
     WTF_LOG(Media, "HTMLMediaElement::stop(%p)", this);
 
-    if (m_playing && m_initialPlayWithoutUserGestures)
-        gesturelessInitialPlayHalted();
+    recordMetricsIfPausing();
 
     // Close the async event queue so that no events are enqueued by userCancelledLoad.
     cancelPendingEventsAndCallbacks();
     m_asyncEventQueue->close();
 
     userCancelledLoad();
 
     // Stop the playback without generating events
     m_playing = false;
     m_paused = true;
@@ skipping 593 matching lines @@
 
     // Enable the first audio track if an audio track hasn't been enabled yet.
     if (audioTracks().length() > 0 && !audioTracks().hasEnabledTrack())
         audioTracks().anonymousIndexedGetter(0)->setEnabled(true);
 
     // Select the first video track if a video track hasn't been selected yet.
     if (videoTracks().length() > 0 && videoTracks().selectedIndex() == -1)
         videoTracks().anonymousIndexedGetter(0)->setSelected(true);
 }
 
+bool HTMLMediaElement::isUserGestureRequiredForPlay() const
+{
+    return m_userGestureRequiredForPlay;
+}
+
+void HTMLMediaElement::removeUserGestureRequirement()
+{
+    m_userGestureRequiredForPlay = false;
+}
+
+void HTMLMediaElement::setInitialPlayWithoutUserGestures(bool value)
+{
+    m_initialPlayWithoutUserGesture = value;
+}
+
+void HTMLMediaElement::notifyPositionMayHaveChanged()
+{
+    m_autoplayHelper.positionChanged();
+}
+
+void HTMLMediaElement::triggerAutoplayViewportCheck()
+{
+    m_autoplayHelper.triggerAutoplayViewportCheck();
+}
+
 #if ENABLE(WEB_AUDIO)
 void HTMLMediaElement::clearWeakMembers(Visitor* visitor)
 {
     if (!Heap::isHeapObjectAlive(m_audioSourceNode))
         audioSourceProvider().setClient(nullptr);
 }
 
 void HTMLMediaElement::AudioSourceProviderImpl::wrap(WebAudioSourceProvider* provider)
 {
     MutexLocker locker(provideInputLock);
@@ skipping 49 matching lines @@
     visitor->trace(m_client);
 }
 
 DEFINE_TRACE(HTMLMediaElement::AudioSourceProviderImpl)
 {
     visitor->trace(m_client);
 }
 #endif
 
 }